Frequency control devices are known to include various types of temperature compensated crystal oscillators. A typical quartz temperature compensated crystal oscillator utilizes several components including a piezoelectric element, an integrated circuit, capacitors, inductors, resistors, etc. These frequency control devices are commonly found in electronic communication devices such as cellular phones, pagers, radios and wireless data devices. Typically, each of these electronic communication devices are available in a range of different models to meet consumer demands for different price and performance levels. Generally, electronic communication devices of different performance levels require functional and performance differences in their temperature compensated crystal oscillators. The need has arisen for a temperature compensated crystal oscillator which is multi-functional and more versatile to meet the changing demands of the marketplace in electronic communication devices, without adding cost.
At its most basic level, a temperature compensated crystal oscillator provides a stable frequency output signal when power is applied to temperature compensated crystal oscillator power inputs. Most temperature compensated crystal oscillators also provide some type of frequency adjustment function for the user. This allows the user to fine tune the output frequency to match their particular communication device requirements. Earlier temperature compensated crystal oscillators were frequency adjusted by the use of an internal variable capacitor which was mechanically adjusted. These oscillators had a tendency to drift which required periodic readjustment.
Later temperature compensated crystal oscillator designs used an integrated circuit (IC) to drive the oscillator and control its frequency. These temperature compensated crystal oscillators can be frequency adjusted by the application of an external DC "warp" voltage by the user. In higher performance temperature compensated crystal oscillator applications, the user may be allowed direct access to the IC of the temperature compensated crystal oscillator by the provision of digital signal input/output leads in the temperature compensated crystal oscillator package. This access allows the user complete control of the frequency functions of the temperature compensated crystal oscillator.
Previously, each of the different types of frequency adjustment functionalities, described above, required different temperature compensated crystal oscillators in different packaging. Therefore, as performance requirements of communication devices changed, different temperature compensated crystal oscillators in different packages were required. Temperature compensated crystal oscillators are commonly manufactured in leadless ceramic packages or in leaded thermoset plastic packages. In each type, the basic temperature compensated crystal oscillator package requires four input/output leads or contacts; one for ground, one to supply power, one for the stable frequency output, and one for the user adjustment of output frequency by the application of a DC "warp" voltage. Higher performance temperature compensated crystal oscillators provide additional input/output leads or contacts which allow user access to the integrated circuit functions of the oscillator. These functions may include the voltage regulator, IC memory, and frequency control functions.
In order to lower the cost of leadless ceramic temperature compensated crystal oscillator packaging, it is common to provide as many input/output contacts as would be required for the highest performance oscillator design or application, or at a minimum, the oscillator design requiring the most input/output contacts. In this way, the same package can be used for most, if not all, of a manufacturer's existing temperature compensated crystal oscillator designs. This approach also allows the temperature compensated crystal oscillator manufacturer the option to assemble all of their oscillators to the highest performance design which are then subject to sorting by performance. Those oscillators passing the high performance specifications can be sold as such. Those oscillators failing the high performance test specifications, but passing the low performance test specifications can be sold as such. The assembly techniques improves manufacturers costs, by reducing scrap. However, lower performance oscillators still retain the input/output connections of the higher performance design. Therefore, a user with lower performance requirements may inadvertently connect the oscillator package improperly and unintentionally input signals which may access, erase or change the IC settings of the oscillator to their detriment. This is a situation which, in the user's view, results in a catastrophic failure.
Similarly, a leaded thermoset plastic temperature compensated crystal oscillator package may be used, and it is common to provide as many input/output leads as would be required for the highest performance oscillator design or application, or at a minimum, the oscillator design requiring the most input/output leads. However, the leaded package has some manufacturing advantages over the leadless ceramic package. First, the package is generally cheaper to produce. Second, changing the package leads for different oscillator designs can be done by changing the leadframe used, without changing the package body. Conversely, there are some problems associated with plastic packaging. First, changing leadframes requires changing the assembly process, also. Second, keeping different leadframe increases inventory. The present invention can solve many of these problems by using one package and leadframe for different temperature compensated crystal oscillator designs by the use of multiple and redundant input/output leads which can be trimmed to alter the available functionality for each user.
A significant portion of the cost of a quartz temperature compensated crystal oscillator is in its packaging. These oscillators typically have higher material and labor costs than a similarly packaged IC. Therefore, oscillator scrap costs due to yield losses are to be avoided if at all possible. Cost reduction can be achieved if the packaging for these oscillators can be simplified without sacrificing yield.
There is a need for a more versatile and improved functionality temperature compensated crystal oscillator package and method for making the same, that: is low cost; has high yield; minimizes inventory; reduces scrap; and is readily manufacturable without custom equipment or added costs.